The company says the facility is now one of Smurfit Kappa's largest and most high-tech packaging plants in Europe.
The investment saw the addition of state-of-the-art machinery at the plant, the company said, and will create 50 new jobs and offer employment to more than 250 staff members.
Chief executive of Smurfit Kappa north-east Europe, Jacek Nieweglowski said, "We are delighted to officially unveil the new manufacturing plant here in Pruszków.
"This project took just over one year to complete and will enable us to continue to pursue our strategic goal of being the supplier of choice to our customers, particularly those looking for the most innovative and sustainable packaging solutions."
The machinery installed in the plant include a high-tech corrugator and a range of ultra-modern converting machinery.
The investment also saw the creation of a new finished goods warehouse, which can accommodate upwards of 12,000 pallets.
The investment will ultimately double the output from the plant, which now spans 37,500 square metres.
The Pruszków packaging plant caters to some of the leading brands in the food and beverage sectors and serves international and local customers.
Saverio Mayer, CEO of Smurfit Kappa Europe added, "This significant investment marks our strategic commitment to our presence in Poland and in Eastern Europe.
"The Pruszków plant is integral to our business and has a talented and skilled workforce fully committed to delivering the best service to our customers."